Simple Relationships for the Optimal Design of Paired Drip Laterals on Uniform Slopes

Microirrigation plants, if properly designed, allow water use efficiency to be optimized and quite high values of emission uniformity to be obtained in the field. It is known that disposing paired laterals, in which two distribution pipes extend in opposite directions from a common manifold, contribute to increasing water use efficiency. Recently, an analytical procedure has been proposed to optimally design paired drip laterals on uniform slopes under the assumption of neglect: (1) the variations of the emitters’ flow rate along the lateral, and (2) the local losses due to the emitters’ insertions. However, this procedure is not readily usable for every geometric and hydraulic characteristic of the lateral and slope fields because it requires solving a system of implicit equations. This study derives simple explicit relationships, reproducing the proposed approach, allowing derivation of the design variables that are required for the optimal design. Moreover, an easy method to determine the best position of the manifold associated to the optimal lateral length on uniform slopes is proposed, making evident a very moderate influence of the geometric and hydraulic characteristics of the lateral. The proposed procedure was successful compared with that derived by the analytical solution. Applications of the proposed relationships, considering different design parameters, are presented and discussed.